38 LABORATORY GUIDE IN BACTERIOLOGY 



Solution for nitrite formation — 



FeS04 0.4 gram 



MgS04 o. s gram 



K2HPO4 I gram 



NaCl 2 grams 



(NH4).S04 I gram 



Distilled water 1,000 c.c. 



Dissolve 20 grams agar in the above solution. 

 After solution add 10 grams precipitated CaCOs- 

 Shake and tube. Sterilize in the autoclave. 



Preparation of silica jelly. — Mix 100 c.c. HCl, 

 specific gravity i.io Beaume's scale at 60° F., with 

 100 c.c. sodium silicate, specific gravity i . 09 Beaume's 

 scale at 60° F. Place in collodion sacs and dialyze in 

 running water for 12 hours. Prepare the following 

 solution: 



(NH4)2S04 0.40 gram 



MgS04 o. OS gram 



KHaP04 o.io gram 



NaaCOj o. 90 gram 



CaCl o.oi gram 



Dissolve these salts in the smallest amount of dis- 

 tilled water possible. Heat both the salt solution and 

 the silica jelly to boiling, cool rapidly without stirring. 

 Mix and pour on petri dishes or tubes and sterilize in 

 the autoclave at 110° C. The tubes should be placed 

 in a slanting position. 



Synthetic agar for plating — 



Dextrose 10 grams 



MgS04 0.2 gram 



KjHP04 0.5 gram 



Pepton o . 05 gram 



Agar 20 grams 



Distilled water 1,000 c.c. 



Dissolve, filter, tube, and sterihze in the autoclave. 



